ACPI: Introduce acpi_bus_power_manageable function

Introduce function acpi_bus_power_manageable() allowing other
(dependent) subsystems to check if ACPI is able to power manage given
device.  This may be useful, for example, for PCI device power
management.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/acpi/bus.c

@@ -295,6 +295,17 @@ int acpi_bus_set_power(acpi_handle handle, int state)
 
 EXPORT_SYMBOL(acpi_bus_set_power);
 
+bool acpi_bus_power_manageable(acpi_handle handle)
+{
+	struct acpi_device *device;
+	int result;
+
+	result = acpi_bus_get_device(handle, &device);
+	return result ? false : device->flags.power_manageable;
+}
+
+EXPORT_SYMBOL(acpi_bus_power_manageable);
+
 /* --------------------------------------------------------------------------
                                 Event Management
    -------------------------------------------------------------------------- */

include/acpi/acpi_bus.h

@@ -335,6 +335,7 @@ void acpi_bus_data_handler(acpi_handle handle, u32 function, void *context);
 int acpi_bus_get_status(struct acpi_device *device);
 int acpi_bus_get_power(acpi_handle handle, int *state);
 int acpi_bus_set_power(acpi_handle handle, int state);
+bool acpi_bus_power_manageable(acpi_handle handle);
 #ifdef CONFIG_ACPI_PROC_EVENT
 int acpi_bus_generate_proc_event(struct acpi_device *device, u8 type, int data);
 int acpi_bus_generate_proc_event4(const char *class, const char *bid, u8 type, int data);